Because providing a better base eduction lets those who are in that 1 SD above category actually use it. There are probably a lot of people right now who are 1 SD above but can't get the education they need to make use of it.
Everything will be fine when everybody is above average...
Historically, the economic promise has been that everyone who CAN get a job will just get a Different job when new technologies make their current jobs obsolete. Plow-pushers will become welders, for example.
And the usual futurist's question is whether instead the low-skill workers are more like horses in the 1930's, soon to be completely useless. The interesting argument in the article is that, well, even if the low-skill workers aren't completely unemployed, they'll be pushed forever into low-productivity industries that are happy enough paying them serf's wages... Perhaps keeping them just busy enough to avoid open revolt. (perhaps.)